That's not graffiti. MIT hackers commonly 'sign in' to places that they've found and gained entrance to. A wiring closet, frankly, is kind of a lame place to sign in at, but the steps under Lobby 7 or the steam tunnels or the little dome are far more interesting, for example.
It's actually looked down upon fairly heavily if a sign in is larger than a regular signature by very much - typically sign ins are lauded, graffiti isn't.
I suspect there won't be as many MIT hackers now that this sort of culture is no longer tolerated. Getting in trouble with your principal/dean/chairman is quite different from facing the secret service, federal prosecution, 30 years in jail and multi-million dollar fines.
MIT over the last few years, sadly, under the Hockfield administration, has screwed hackers over - no doubt about that. Numbers decreased because of that. But they increased at the same time due to the MIT blogs and better (sometimes unintentional) publicity of MIT hacks.
I honestly suspect that things will be better for hackers under Reif's administration. He does, in my humble opinion, "not suck."
EDIT: Also important of note is that Aaron wasn't a student at MIT - historically, MIT students were forgiven for things like hacking, but non-MIT students were typically handed over to Cambridge Police. Typically, when hacking with a non-MIT student, you would pretend they were a 'pre-frosh' if you could.
